Check for null before dereffing.

src/VisualStudio/Core/Def/Implementation/Workspace/VisualStudioAddMetadataReferenceCodeActionOperationFactoryWorkspaceService.cs

@@ -53,7 +53,10 @@ public override void Apply(Workspace workspace, CancellationToken cancellationTo
                     // This is the same approach done in CVBErrorFixApply::ApplyAddMetaReferenceFix
 
                     var uiHierarchy = visualStudioWorkspace.GetHierarchy(_projectId) as IVsUIHierarchy;
-                    OLECMD[] command = new OLECMD[1];
+
+                    if (uiHierarchy != null)
+                    {
+                        var command = new OLECMD[1];
                         command[0].cmdID = (uint)VSConstants.VSStd2KCmdID.ADDREFERENCE;
 
                         if (ErrorHandler.Succeeded(uiHierarchy.QueryStatusCommand((uint)VSConstants.VSITEMID.Root, VSConstants.VSStd2K, 1, command, IntPtr.Zero)))
@@ -65,6 +68,7 @@ public override void Apply(Workspace workspace, CancellationToken cancellationTo
                         }
                     }
                 }
+            }
 
             public override string Title
             {